How will a bass damage a guitar amp?

mambo4 · #1 03-24-2011, 05:56 PM

A common response to "can I play my bass thru a guitar amp?"
seems to be "yes, but you might harm the speakers"
(after "yes, but it will sound bad" -but I'll ignore asthetics for discussion)

So can someone explain the mechanics of how bass will damage a guitar amp?
If I roll off the lows on teh guitar amp, will this prevent it?

will33 · #2 03-24-2011, 06:17 PM

You won't damage the amp but you most certainly can blow the speaker, especially if it's an openback type guitar cab....or any guitar cab for that matter with any appreciable power or bass boost going into it. Guitar speakers just plain ain't made to handle lower frequencies with power behind them. It can be done either at low volumes with the bass rolled off as you say....or with 8 or 16 guitar speakers to divide up the power so each individual one isn't seeing that much, as in the earliest ampeg dual 810 rigs. Another way to do it is to use a crossover and run your deep lows and lowmids clean to a bass cab and run middle and higher frequencies through a guitar rig as they're fine with handling that. Guitar speakers are also made to distort early as it's part of the sound so it's not easy to tell if you're stressing the speakers or not......until they go silent, that is.

Russell L · #3 03-24-2011, 06:33 PM

But you can do the reverse. I played guitar for years through a Fender Bassman (early 60s blackface) into two EV SRO 12s in a big cab. Awesome! No wonder I can't hear.

skruch · #4 03-24-2011, 06:38 PM

A bass speaker has an available cone excursion of 1/4". A guitar speaker has an available cone excursion of 1/8". Nuff said.

oldbassplayergu · #5 03-24-2011, 06:54 PM

but a fender "bassman" is more a guitar amp than bass anyway. by that I mean bass amp tech at the time were not what they are now. I hate to agree with jimmy m but ampeg was the only co. that had a clue about bass amps or maybe sunn.

billfitzmaurice · #6 03-24-2011, 08:07 PM

Quote:

A bass speaker has an available cone excursion of 1/4". A guitar speaker has an available cone excursion of 1/8".

Not even. A good bass driver has about 5mm xmax, the average guitar driver 1mm or less.

bdplaid · #7 03-24-2011, 08:12 PM

Using the proper amount of pressure, a guitar amp can be sufficiently damaged by a blow from a bass to yield it inoperable, yet merely scratching the bass. It takes much practice for proficiency, and is recommended for optimal ensemble sound.

D.A.R.K. · #8 03-24-2011, 08:14 PM

I've been playing through a Marshall 4x12 b guitar cab for a few years now, tons of fx and high volumes (300 watt walkabout head). I have yet to blow a speaker. I did replace a pair of the celestion 75's with vintage 30's for more bottom. If I tried, I'm sure I could shred the speakers. But then again, I've shredded plenty of bass specific speakers already. Just thought i would share my experience.

BZadlo · #9 03-24-2011, 08:15 PM

Plenty of people have done it successfully for years.
Lemmy
Cliff Burton
The dude from High on Fire
Robert Trujillo
The dude from Death From Above 1979
etc
You just have to be careful and watch how much the speakers are moving.

**nutdog** · #10 03-24-2011, 08:16 PM

Quote:

Originally Posted by bdplaid

Using the proper amount of pressure, a guitar amp can be sufficiently damaged by a blow from a bass to yield it inoperable, yet merely scratching the bass. It takes much practice for proficiency, and is recommended for optimal ensemble sound.

AwkwardLoudness · #11 03-24-2011, 08:50 PM

At high volume with bass frequencies, most guitar speakers will fart out and likely be damaged. For bassists who like to dial in with little or no low end, it's less of an issue...well, depending on the speaker.

Quote:

Originally Posted by skruch

A bass speaker has an available cone excursion of 1/4". A guitar speaker has an available cone excursion of 1/8". Nuff said.

Excursion varies among speakers for both guitar and bass. Eminence Kappalite 3015LF has 9.6 mm excursion = 0.38" = approx 3/8".

Quote:

Originally Posted by D.A.R.K.

I did replace a pair of the celestion 75's with vintage 30's for more bottom.

It would surprise me if one could get much low end out of vintage 30s.

Alex1984 · #12 03-24-2011, 09:04 PM

I've heard G12T75s in a Marshall 1960 that actually sounded ok with bass.

That said, I still worry about pumping bass through PA cabs without a proper crossover.

D.A.R.K. · #13 03-24-2011, 09:11 PM

Quote:

Originally Posted by AwkwardLoudness

At high volume with bass frequencies, most guitar speakers will fart out and likely be damaged. For bassists who like to dial in with little or no low end, it's less of an issue..

It would surprise me if one could get much low end out of vintage 30s.

Surprise, the cab sounds quite good, with nice usable lows. I realize it's limits, it's no sub cab, but the 30s go much deeper than the 75s. I got this originally for my piccolo basses, but tried my standard bass through it and was floored at how good it sounds, didn't think it would, but there you go. Keeps up in a loud trio without issue. I would think it might be disappointing with a low b, however.

will33 · #14 03-24-2011, 09:11 PM

This shtuff is gettin' sideways.

Can you play a bass through a guitar amp? Why, yes you can. I just did the other night....with a P and a valve jr.....with an open back cab....at low volumes....like mixing with an un-miced acoustic and an un-miced voice.

Can you do it at appreciable volumes like at a real gig with a full band with real equipment?......NO.....at least not if you would like to preserve your guitar amp.

TN WOODMAN · #15 03-24-2011, 09:16 PM

Been playing guitar since '69, bought my first bass in '06 (fretless jazz, another fretless jazz, fretted jazz and fretted p since) and initially tried playing through my guitar amps at low levels (Fender De Luxe and Blues De Ville with 4 10s). At bedroom levels sounded pretty good but I was constantly worried about blowing a speaker. Bought the Markbass Berlin Combo in short order and love it. Powerful and light, and a single 15. Now all I need is the NY151 extension cab and I'm set.

Downunderwonder · #16 03-24-2011, 09:23 PM

I put bass into a marshall guitar cab with 4x12 once. It sounded lousy and we didn't turn it up because it wouldn't have got any better, it would have blown the speakers.

Into a small guitar combo at low volume it sounded quite ok. I would never attemp to gig with it unless guitars were un amplified.

Stumbo · #17 03-24-2011, 09:23 PM

Quote:

Originally Posted by mambo4

If I roll off the lows on teh guitar amp, will this prevent it?

Maybe.

onosson · #18 03-24-2011, 09:36 PM

I've done it twice in full-band gig situations, with two different open back guitar amps: a Fender Blues DeVille (original version with blue alnico speakers), and a Vox AD50VT. Both definitely suffered in terms of available low end, but they worked for the situation at the time. I actually really like the tone through the DeVille.

longfinger · #19 03-24-2011, 09:47 PM

In regards to guitar combos, isn't the amp and speaker matched, so that a combo's speaker is designed to handle whatever signal a combo's amp can dish out? (Speaker cone being "overbuilt" in regards to its paired amp?) Guitar combo makers don't want their customers blowing speakers and crying about it either. Would not the guitar amp also have some built in HPF at 70HZ or something to reduce low frequency noise and conserve power to the frequencies the guitar uses?

jamminjh · #20 03-24-2011, 11:56 PM

Yah know? It would be great if companies like Fender, Vox, Marshall, Mesa, etc... would make great sounding all tube combo amps FOR bass like they have with the AC30, the Deville, and all the others... Why are we so often lacking in variety at moderate cost? Why do we have to pay 2 to 3 times as much for 2 channeled tube amps with built in reverb and trem?

Where is our stuff?! How come guitarists get stuff and we don't got no stuff?!